X-ray properties of the Northern Galactic Cap AGNs in the 58-month Swift-BAT catalog

TL;DR

This study provides a comprehensive X-ray spectral analysis of 100 AGNs in the Northern Galactic Cap from the Swift-BAT catalog, revealing their absorption properties, spectral features, and contributions to the X-ray background.

Contribution

It offers the first detailed spectral analysis of a complete, low-redshift AGN sample in this region, expanding understanding of AGN properties beyond previous surveys.

Findings

60% of AGNs are obscured with high column densities.

Approximately 9% are Compton-thick sources.

Soft excess is either well-detected or absent, indicating diverse origins.

Abstract

We present a detailed X-ray spectral analysis of a complete sample of hard X-ray selected AGN in the Northern Galactic Cap of the 58-month Swift Burst Alert Telescope (Swift/BAT) catalog, consisting of 100 AGN with b>50deg. This region has excellent potential for further study due to the availability of a wide range of archival multi-wavelength data, and we propose it as a low-redshift analog to the `deep fields' work on AGN at higher redshifts. We present distributions of luminosity, absorption, and other key quantities, from fitting new and archival X-ray data gathered from XMM-Newton, Swift/XRT, ASCA and Swift/BAT. We probe to deeper redshifts than the 9-month BAT catalog (<z>=0.043), and uncover a broader absorbing column density distribution. The fraction of obscured (log N_H >= 22) objects in the sample is ~60%, and 43--56% of the sample exhibits `complex' 0.4--10keV spectra. The soft excess is either well-detected in AGN or undetected, suggesting that the process responsible for producing the soft excess is not ubiquitous. The fraction of Compton-thick sources in our sample is ~9%, and `hidden/buried AGN' constitute ~14% of our sample. Compton reflection is found to be important in a large fraction of our sample using joint XMM-Newton+BAT fits (reflection amplitude <R> = 2.7 +/- 0.75), indicating light bending or extremely complex absorption. The average 1--10keV spectrum for the sample reproduces the 1--10keV X-ray background slope as found for the 9-month BAT AGN sample. The completeness limit for the sample is ~4 times fainter than that for the 9-month catalog (abridged).